One thing about the Bye Bye Sky High scene is that Oliver professes to have really loved Bertie, so you would think he would have been a bit more kind to Bertie considering that it would be his last moments alive.

One thing that always seemed odd about Oliver's preparation for the murder is that when he is setting up the umbrella upstairs prior to the murder, he is almost giddy, presumably with how clever his set up is. However, I find it hard to fathom that anyone who is about to murder their closest friend, or even the fact that they are about to cross the line into an unthinkable act no matter who the victim, would not be giddy - they would be nervous, contemplative, distressed, but not giddy.